Modular vs. Manufactured. Why the difference matters.

Legally and structurally identical to site-built. Same building code (CBC), same engineering standards, same legal category (real property), same plan check at your local building department. Once installed, a modular unit is — by law and by spec — site-built.

A separate category, legally and structurally. Built to the federal HUD code (24 CFR Part 3280) which preempts state code. Defaults to personal property (DMV-style title). Different engineering rubric. Conversion to real property under HCD Form 433A is a legal/financing fix but does not retroactively make the structure CBC-compliant.

Built to the California Building Code and Title 24 — the same code as site-built. HCD's Factory-Built Housing program certifies the factory; your local jurisdiction does the standard plan check and inspects the site work.

Built to the federal HUD code. HUD-approved third-party agencies (DAPIA / IPIA) certify the factory under federal authority. Local jurisdictions cannot re-inspect the federally certified portions — but typically do add site, foundation, and design-compatibility review.

No chassis, no transport-imposed federal design rules. Two-story and three-story configurations, basements, garage-under, cathedral ceilings, full-spec roof designs (flat, gabled, butterfly, steep pitch), large open spans, custom architecture for the lot.

Constrained by a steel chassis, transport width and height limits, and federal design rules. Typically single-story, limited roof pitch options, narrower open spans, fewer cathedral/multi-story options. Designs come largely from a catalog of HUD-approved models.

Installed on any standard permanent foundation — slab, crawl, basement, even a 2-car garage underneath. No steel chassis. Visually and structurally indistinguishable from site-built once installed.

Built on a permanent steel chassis that never leaves the structure. Set on a HUD-approved foundation system — typically piers with skirting, or per HCD Form 433A on a CBC-engineered permanent foundation. Basement and garage-under configurations are rare and harder to permit.

Built to California Title 24 for the specific climate zone your unit installs in — heat-pump-ready, high-performance envelope, solar-ready per the most recent code cycle.

Built to the federal HUD thermal envelope standard, which is less stringent than CA Title 24 in most California climate zones. Some manufacturers offer a CA-spec upgrade package; many do not.

Eligible for conventional 30-year mortgages, FHA, VA, and construction-to-perm — same lenders, same rates as site-built. Standard homeowners (HO-3) insurance. Real property from day one.

When installed on a permanent foundation and titled as real property via HCD Form 433A, manufactured homes qualify for conventional mortgages at the same rates as site-built. Without 433A conversion, financing defaults to a chattel loan (typically 1–3 points higher, 20–25 year terms). Lender pool is narrower; secondary-market criteria are more restrictive even after conversion.

Eligible everywhere site-built is eligible. SB 1211 and the broader CA ADU statute treat modular the same as site-built — same plan check, no extra design-compatibility findings.

Eligible under CA Gov Code § 65852.2 when installed on a permanent foundation per HCD Form 433A. Many jurisdictions impose additional design-compatibility standards on HUD-code ADUs (minimum roof pitch, exterior materials, eave overhangs, siting). In practice, modular has fewer friction points and is the more common path for CA ADUs.

Comps to site-built homes in the local market. Appreciates with the surrounding real estate. No buyer-side stigma; appraisal and underwriting treat it as site-built.

Comps to other manufactured homes, not site-built. Appreciation is constrained by the smaller comp pool. 433A-converted units behave closer to site-built but still face appraisal and buyer-perception headwinds in many submarkets.